With regard to the background of the invention, it is noted that catheters having so-called drug-eluting stents are known from the prior art in which only solids are used as pharmaceutical active substances. Typical approaches for providing an active substance on or in stents involve incorporation of the active substance into a polymer support, introduction into a porous surface, or integration into active substance depots on the stent. These technical designs are tailored to solids, since for mechanical reasons liquid substances cannot be permanently applied to the stent surface. In addition, compounds in a liquid substance in the stent cause fundamental difficulties with regard to stability under storage. For example, drying phenomena or demixing effects may occur.
Approaches to coating medical implants, in particular stents, with liquids are known from US 2006/0124056 A1 or EP 1 325 758 A2. The first-referenced document discloses a device for applying active substances to surfaces of medical implants, in particular stents, composed of a base station and an exchangeable cartridge. A holder for the stents is provided on the cartridge, by means of which the active substances are sprayed via a nozzle onto the surface of the stent. A drive unit is provided on the base station which moves the stent holder and the nozzle relative to one another, the aim being to ensure defined wetting of the stents with liquid active substance.
In the second-referenced document, the aim is to improve the dosing accuracy for the liquid medicament on the stent by applying a potential difference between the spray unit and the stent.
A problem with the above approaches is that, immediately before placement of the catheter together with the stent, a surgeon must coat the stent with the active substance solution. For this purpose the stent has a porous surface onto which a solution of alcohol and rapamycin, for example, is sprayed. This is a complicated and time-consuming procedure in the surgical environment, in which the dosing of the liquid active substance is very imprecise.